Taxonomic and Stratigraphic Significance of the Dispersed Spore Genus Calamospora

Abstract

In situ spores are described from Pennsylvanian-age sphenopsid cones. Spores from cones referable to the plant Calamites have been shown to resemble the dispersed spore genera Elaterites, Vestispora, or Calamospora at different stages in spore ontogeny. Spores from some cones referable to the plant Sphenophyllum have ontogenetic stages resembling Vestispora and Calamospora indicating that these two dispersed spore genera were produced by more than one type of plant. To date, features used to delimit species of dispersed Calamospora-like spores have included spore diameter, presence or absence of dark contact areas, distribution and arrangement of compression folds, minute wall ornamentation, presence of a globular inner body, separation of presumed outer and inner exine layers, and length of trilete arms. Results of the present investigation indicate that none of these features can be used to distinguish between spores produced by different cone species. The wide range of variation in these features among spores obtained from different specimens of the same cone species, and even from the same cone specimen, suggest that a clearcut division of species within the dispersed spore genus Calamospora is not possible. Caution should be used in making stratigraphic determinations based largely from dispersed spores that resemble Calamospora, Elaterites, Vestispora, Schopfites, Phyllothecotriletes, Ricaspora, and Perotriletes.